I HATE my credit card. I am trying to pay the balance off (it's down to about £800 now) as it costs me around £20 in interest.
I would have thought that if you can afford to pay the balance off each month - what is the point of having a credit card, you may as well pay on your debit card...

To answer the initial question, you do have an interest free period but it depends on your statement date and when you make the purchase.

(this is all coming from a UK perspective, but I'm sure CCs are the same rip-off the world over)

Say your statement date is 31 July and your previous statement was on 30 June, and you have a nil balance. You'll have something like 3 weeks (perhaps it varies between providers) after your 31 July statement to make a payment (be it payment in full or a part-payment). So if you make a purchase on 1 July, that will appear on your 31 July statement and your deadline for a payment is 21 days later. After that payment deadline, they will begin to apply interest. So you'd have a maximum of 52 days of interest free credit on that purchase. If you pay in full within that time, you'll suffer no interest obviously. If you make a part payment with a balance rolling over onto your next statement, you're going to see interest being applied to the balance. Whereas, if you buy something like two days before your statement is issued, you're only going to have a little over 3 weeks interest free period.

Obviously you want to find the best interest rate you can get, but it's also worth looking into how your interest is actually applied and finding the fairest one. I don't know about anywhere else but here in the UK it can vary for different providers. Some calculate interest on a daily basis on the balance on each day and then apply the total of all those daily interests on the statement date. This is slightly more of a rip off depending on how you pay. Some apply a month's worth of interest on the balance on the day of the statement, which is less of a rip off. I'll try to illustrate it better:

Example 1: you have exactly a £1,000 balance at 30 June (which say, for ease of explanation, has rolled forward from previous months and already includes previous interest) and a 20% interest rate. Your provider calculates interest daily. You pay the whole £1,000 on 15 July. You'll see 15 days worth of interest on your £1,000 being applied on your 31 July statement - roughly about £8, which you'll then have to pay. Of course, because that £8 balance is rolling forward now, they'll apply interest on that too so if you pay that £8 on 15 August, you'll have 15 days worth of interest being applied on it at your next statement date - it'll be mere pennies but you can see how ridiculous it can get. And they'll want that payment, even though it's such a paltry amount.

Example 2: you have exactly the same balance and interest rate as above but your provider calculates and applies interest monthly on the balance at the statement date. You pay the whole £1,000 on 15 July. You'll have a nil balance at 31 July and therefore no interest to pay.

See what I mean? It's worth looking into that too, if you're likely to end up having a balance rolling forward. These CC providers can be real bastards.

wtf are temporary authorizations?? i have 3 on my credit card right now, and those have taken like $50 from my credit card because of it. i should only owe $100 but now i owe $150 because of temporary authorizations, wtf. its like visa took money from me on the purchases i made with my credit card

Because of that interest free period (which, as I said in my post above, can be up to 52 days). If you make a big purchase of, say, £1,000 and you already have money available to pay for it, you can keep your money in your bank account and earn interest on that, while you're getting no interest charged on the purchase on your credit card. And if you pay it off within the interest free period, you've earned interest on your own money (while being charged no interest on the credit card), which you wouldn't have done if you'd put the purchase straight on your debit card. But it only makes sense for big purchases. You're obviously not gonna earn much interest on £5 you had available to buy a pack of cigarettes, by sticking the purchase on your credit card.

Oh it makes a bit more sense to me now